1. Field of the Invention
The present invention generally relates to a guide device for moving sheet material in printing presses, which guide device, by means of blown air, presses the sheet material flat or smoothly against the shell of a transporting drum or of a cylinder, essentially without any contact between the sheet material and the guide device.
2. Background Information
A similar device is disclosed in German Patent No. 30 44 649 C2 which corresponds to U.S. Pat. No. 4,384,524, wherein a smoothing or blowing device with a blast chamber for applying or pressing a sheet against a printing cylinder or a sheet transfer drum uses blown air to press sheets against the external surface of rotating cylinders or sheet transfer drums. The blowing device extends over the width of the printing press and is located at a defined distance from the cylindrical surface of the printing cylinder or of the sheet transfer drum. The application thereby achieved is effective essentially only to a limited extent, and can become altogether ineffective as soon as the end of the sheet moves away from the vicinity of the blast chamber.
An additional device which is used to press the sheet flat is disclosed in German Patent No. 39 20 730 C2, which corresponds to U.S. Pat. No. 5,086,698. This device uses a blast nozzle which directs a current of air onto the sheet material, thereby achieving a brushing or flattening effect. Here again, it is essentially impossible to reliably prevent a relaxation of the sheet material and thus uneven contact with the cylinder, in particular when thin sheet material is used.